Strange magtape anecdote

[Paul Koning]

> On Oct 27, 2020, at 11:08 AM, Dave Wade G4UGM via cctalk <cctalk at classiccmp.org> wrote:
> 
> ...
> I remember when doing standby power generator tests we had to remember to off-line all the drives at end of job, other wise they all tried to rewind at the same time....
> .. and the generator could comfortably do two, stuttered a bit with three, but on the first test as the fourth flicked in there was a big "bang" and lots of flapping of tape, plus lots of cursing from our Site Engineer.,,,,

A similar issue shows up with large collections of disk drives.  That includes modern small HDDs.  The motor start surge current is a lot higher than the steady state current, so starting a row of drives all at once -- or a box full of 3.5 inch HDDs in a modern storage array -- can cause an overload.

In storage array firmware that's dealt with by spinning up the drives a couple at a time, fewer at a time if one of the power supplies has failed.

	paul